Asymptomatic Malaria Infections Research Articles

Prevalence of Asymptomatic Malaria and Demographic Influences Among Primary School Children in Dala, Kano State, Nigeria

Malaria poses a significant health challenges globally, disproportionately affecting vulnerable population such as children. This study  aimed to ascertain the prevalence of asymptomatic malaria among primary school pupils in Dala Local Government Area, Kano State,  Nigeria. Utilizing a crosssectional design, blood samples were collected from 107 pupils through finger prick. These samples were then  subjected to microscopic examination following the preparation of both thin and thick blood films. The overall prevalence of  asymptomatic malaria was found to be 21.5%, with 23 pupils testing positive for the parasite. Gender-wise, male participants exhibited a  higher infection rate (73.9%) compared to their female counterparts (26.08%). Age-specific analysis revealed that the 13-16 years age  group had the highest prevalence of asymptomatic malaria at 73.9%, whereas the 5-8 years age group had the lowest at 2.38%. These  results highlighted the substantial presence of asymptomatic malaria among school-aged children, particularly within the 13-16 years age  bracket. The study underscores the need for targeted public health interventions to identify and treat asymptomatic malaria  infections in order to mitigate the silent transmission within this vulnerable population. 

Association between asymptomatic Plasmodium falciparum malaria infection, anaemia and mean corpuscular volume of school children in the Volta Region of Ghana.

Although, several studies have reported abnormal Mean Corpuscular Volume (MCV) values and anaemia associated with malaria infections with a focus on Plasmodium falciparum among patients with complicated and uncomplicated malaria, none has looked at the association with asymptomatic malaria. This study aimed to assess this association. We conducted a cross-sectional study using 3 mL of blood samples from 549 children aged 5-17 years attending 5 schools selected in the Volta Region. Semi-structured questionnaires were administered to the children to obtain demographic data. Blood samples were collected to estimate the children's full blood count (FBC) and malaria status. Data obtained wereanalysed using STATA 15 software. P-values of less than 0.05 were considered statistically significant. Most of the children inthis study (49.9%) had normal MCV (81.3-91.3 fL) with an overall malaria prevalence of 55.6%(95% CI: 51.3-59.8) and anaemia prevalence of 48.6% (95% CI 44.4-52.9). Most anaemic children had normal MCV (81.3-91.3 fL) (49.8, 95% CI 43.7-56.0). The predicted probability of malaria was highly likely among children with normal MCV (81.3-91.3 fL) but with high variability and uncertainty among those with low MCV (<81.3 fL) and high MCV (>91.3 fL). This study shows a reduced predicted probability of malaria among children with low and high MCV, playing a protective function against malaria. Further studies are required to elucidate the interaction.

Utilization of malaria preventive strategies among pregnant women at Adeoyo Maternity Teaching Hospital, Ibadan, Nigeria

INTRODUCTION: Malaria in pregnancy is associated with a high rate of maternal and perinatal morbidity and mortality. Utilization of preventive strategies during pregnancy is an integral part of controlling the burden of malaria in pregnancy. This study evaluated the malaria preventive strategies utilized and the prevalence of asymptomatic malaria among pregnant women at Adeoyo Maternity Teaching Hospital (AMTH), Ibadan, Nigeria.&#x0D; METHODS: A facility-based descriptive cross-sectional study among 223 pregnant women in Adeoyo Maternity Teaching Hospital, Ibadan, Nigeria. Information on socio-demographic and obstetric characteristics, malaria symptoms, and the preventive strategies utilized were obtained using a structured questionnaire. Descriptive and bivariate analysis using chi-square test and multivariate analysis at 95% confidence interval and p&lt; 0.05 was used to determine the predictors of asymptomatic malaria infection in relation to socio-demographic characteristics and malaria preventive strategies utilized.&#x0D; RESULTS: The mean age was 30±5 years. More than half (53.4%) of them used insecticide-treated nets consistently, 49.3% sprayed the room regularly with insecticides, while the majority (88.3%) reported they maintained a clean environment. However, 11.7% tested positive for the malaria parasite. Consistency in the use of insecticide-treated net (ITN) and participants age were factors associated with malaria occurrence (p=0.01). The use of ITN and being &gt;30 years of age are protective factors against having malaria infection among pregnant women (AOR= 0.34; 95%, CI=0.14-0.84) and (AOR=0.31; 95% CI=0.13-0.76) respectively.&#x0D; CONCLUSION: Irrespective of all other malaria preventive strategies adopted by pregnant women, consistent use of ITN was independently a protective factor against developing malaria in pregnancy.

Asymptomatic Malaria among Pregnant Women Attending Ante-Natal Clinic in Osogbo, Nigeria

Background: Pregnant women are in danger from malaria infection during pregnancy, which is a serious public health issue. A key obstacle to eradicating malaria is the reservoir host for the parasite, and is also regarded as one of the main obstacles to eliminating malaria. This study assessed the prevalence of asymptomatic malaria and associated factors among pregnant women attending antenatal clinics in Osogbo, Southwestern Nigeria. Methods: A hospital-based cross-sectional study was conducted between July and October 2020 to assess the prevalence and predictors of asymptomatic malaria among 294 consenting pregnant women. Socio-demographic data, Intermittent Preventive Treatment in pregnancy with SP (IPTp-SP), and information on insecticide-treated nets use were collected using a structured questionnaire. SD BIOLINE Malaria rapid diagnostic test kits and Giemsa-stained blood smear microscopy were used to diagnose Plasmodium infections. Anaemia status was determined using microhematocrit centrifugation. Data were analysed using SPSS version 20.0 statistical software. In all comparisons, p-values ≤ 0.05 were considered statistically significant. Results: The prevalence of asymptomatic malaria infection was 20.4% (60/294) and 23.5% (69/ 294) using microscopy and RDT, respectively. Among those infected, 76.7% were anaemic (p=0.001). Asymptomatic malaria was significantly associated with not using insecticide-treated bed nets (ITN). Secundigravida women and being in third-trimester pregnancy were significant determinants of pregnancy-associated malaria. Conclusion: This study showed that malaria and anaemia are still prevalent among pregnant women in Southern Nigeria, and it is a significant concern for public health. Improved access to intermittent preventive treatment with sulphadoxine-pyrimethamine and the use of long-lasting insecticidal nets should be encouraged to help further diminish the risk of malaria infection amongst pregnant women in the region.

Association between asymptomatic Plasmodium falciparum malaria infection, anemia and mean corpuscular volume of school children in the Volta Region of Ghana

Abstract Introduction/Objective Although several studies have reported abnormal MCV values and anemia associated with malaria infections with a focus on P. falciparum among patients with complicated and uncomplicated malaria. This study assessed the association between asymptomatic P. falciparum malaria infection, anemia, and the MCV values of school children in Ghana. Methods/Case Report We conducted a cross-sectional study using 3 ml of blood samples from 549 children aged 5- 17 years attending 5 schools selected in the Volta Region. Semi-structured questionnaires were administered to the children to obtain demographic data. Blood samples were collected into a K2EDTA tube and then used to estimate the children’s automated full blood count (FBC) and malaria status using microscopy. MCV was classified into low, normal, and high. Data obtained were analyzed using STATA 15 software. P-values less than 0.05 were considered statistically significant. Results (if a Case Study enter NA) Most of the children in this study (49.9%) had normal MCV (81.3-91.3 fL) with an overall malaria prevalence of 55.6 % (95% CI: 51.3-59.8) and anemia prevalence of 48.6% (95% CI 44.4-52.9). The majority of the anemic children had normal MCV (81.3-91.3 fL) (49.8, 95% CI 43.7-56.0). The predicted probability of malaria was highly likely among children whose MCV fell within the first and third quartiles. Conclusion This study shows a reduced predicted probability of malaria among children with low and high MCV, playing a protective function against malaria. Further studies are required to elucidate the association and interaction between MCV, anemia, and asymptomatic Plasmodium falciparum infection.

Asymptomatic and submicroscopic malaria infections in sugar cane and rice development areas of Ethiopia

BackgroundWater resource development projects, such as dams and irrigation schemes, have a positive impact on food security and poverty reduction. However, such projects could increase prevalence of vector borne disease, such as malaria. This study investigate the impact of different agroecosystems and prevalence of malaria infection in Southwest Ethiopia.MethodsTwo cross-sectional surveys were conducted in the dry and wet seasons in irrigated and non-irrigated clusters of Arjo sugarcane and Gambella rice development areas of Ethiopia in 2019. A total of 4464 and 2176 study participants from 1449 households in Arjo and 546 households in Gambella enrolled in the study and blood samples were collected, respectively. All blood samples were microscopically examined and a subset of microscopy negative blood samples (n = 2244) were analysed by qPCR. Mixed effect logistic regression and generalized estimating equation were used to determine microscopic and submicroscopic malaria infection and the associated risk factors, respectively.ResultsPrevalence by microscopy was 2.0% (88/4464) in Arjo and 6.1% (133/2176) in Gambella. In Gambella, prevalence was significantly higher in irrigated clusters (10.4% vs 3.6%) than in non-irrigated clusters (p < 0.001), but no difference was found in Arjo (2.0% vs 2.0%; p = 0.993). On the other hand, of the 1713 and 531 samples analysed by qPCR from Arjo and Gambella the presence of submicroscopic infection was 1.2% and 12.8%, respectively. Plasmodium falciparum, Plasmodium vivax, and Plasmodium ovale were identified by qPCR in both sites. Irrigation was a risk factor for submicroscopic infection in both Arjo and Gambella. Irrigation, being a migrant worker, outdoor job, < 6 months length of stay in the area were risk factors for microscopic infection in Gambella. Moreover, school-age children and length of stay in the area for 1–3 years were significant predictors for submicroscopic malaria in Gambella. However, no ITN utilization was a predictor for both submicroscopic and microscopic infection in Arjo. Season was also a risk factor for microscopic infection in Arjo.ConclusionThe study highlighted the potential importance of different irrigation practices impacting on submicroscopic malaria transmission. Moreover, microscopic and submicroscopic infections coupled with population movement may contribute to residual malaria transmission and could hinder malaria control and elimination programmes in the country. Therefore, strengthening malaria surveillance and control by using highly sensitive diagnostic tools to detect low-density parasites, screening migrant workers upon arrival and departure, ensuring adequate coverage and proper utilization of vector control tools, and health education for at-risk groups residing or working in such development corridors is needed.

Schoolchildren with asymptomatic malaria are potential hotspot for malaria reservoir in Ethiopia: implications for malaria control and elimination efforts

BackgroundSchoolchildren with asymptomatic malaria infections often go undiagnosed and untreated, serving as reservoirs for infection that hamper malaria control and elimination efforts. In this context, little is known about the magnitude of asymptomatic malaria infections in apparently healthy schoolchildren in Ethiopia. This study was aimed at determining the prevalence of asymptomatic malaria infection and its associated factors in apparently healthy schoolchildren in Ethiopia.MethodsFrom September 2021 to January 2022, a school-based cross-sectional study was conducted on 994 apparently healthy schoolchildren (aged 6–15 years) selected from 21 primary schools in the Gomma district, of Jimma zone, southwestern Oromia, Ethiopia. A multi-stage sampling technique was used to select schools and participants. After allocating the total sample proportionally to each school and then to each grade, participants were selected using the lottery method from a list of student records (rosters). Finger-pricked blood samples were collected for microscopy blood film preparation and malaria rapid diagnostic test (RDT) (SD Bioline Malaria Ag Pf/Pv). Moreover, dry blood spots (DBSs) were prepared onto filter papers for quantitative real time polymerase chain reaction (qPCR) analysis.ResultsAs determined by RDT and microscopy, the prevalence of asymptomatic malaria was 2.20% and 1.51%, respectively. Using qPCR, the overall prevalence was 5.03% (50/994). Of this, Plasmodium falciparum, Plasmodium vivax and mixed infections accounted for 90%, 6% and 4%, respectively. Submicroscopic asymptomatic malaria infection was also accounted for 70% (35/50) of the overall prevalence. Household head age, nighttime outdoor activities of household heads, family history of malaria, absence of insecticide-treated nets (ITN), and presence of stagnant water around the houses are all significantly associated with asymptomatic malaria infections among schoolchildren.ConclusionsThis study found that both RDT and microscopy underestimated the prevalence of asymptomatic malaria in schoolchildren. However, qPCR was able to detect even low levels of parasitaemia and revealed a higher prevalence of asymptomatic submicroscopic malaria infections. The findings imply that schoolchildren with asymptomatic malaria infection are potential hotspot for malaria reservoir that fuels ongoing transmission. Therefore, it is imperative to include schoolchildren and schools in malaria intervention package and equally important is the adoption of more advanced and sensitive diagnostic tools, which would be crucial for successful malaria control and elimination efforts. Targeted interventions for asymptomatic malaria-infected schoolchildren can provide invaluable support to the National Malaria Control Programme in controlling and eventually eliminating the disease.

Implications of asymptomatic malaria infections on hematologic parameters in adults living with HIV in malaria-endemic regions with varying transmission intensities

ObjectivesHIV and malaria coinfection impacts disease management and clinical outcomes. This study investigated hematologic abnormalities in malaria-asymptomatic people living with HIV (PLHIV) in regions with differing malaria transmission. MethodsStudy participants were enrolled in the African Cohort Study: two sites in Kenya, one in Uganda, and one in Nigeria. Data was collected at enrollment and every 6 months. Logistic regression estimated odds ratios for associations between HIV/malaria status and anemia, thrombocytopenia, and leucopenia. ResultsSamples from 1587 participants with one or more visits comprising 1471 (92.7%) from PLHIV and 116 (7.3%) without HIV were analyzed. Parasite point prevalence significantly differed across the study sites (P <0.001). PLHIV had higher odds of anemia, with males at lower odds compared to females; the odds of anemia decreased with age, reaching significance in those ≥50 years old. Participants in Kisumu, Kenya had higher odds of anemia compared to other sites. PLHIV had higher odds of leucopenia, but malaria co-infection was not associated with worsened leucopenia. The odds of thrombocytopenia were decreased in HIV/malaria co-infection compared to the uninfected group. ConclusionHematological parameters are important indicators of health and disease. In PLHIV with asymptomatic malaria co-infection enrolled across four geographic sites in three African countries, abnormalities in hematologic parameters differ in different malaria transmission settings and are region-specific.

Prevalence and predictors of asymptomatic malaria infection in Boricha District, Sidama Region, Ethiopia: implications for elimination strategies

BackgroundMalaria remains a major public health threat in Ethiopia despite the tremendous progress made towards the 2030 elimination targets. The silent transmission of asymptomatic infection is one of the factors that enhance the persistence of the disease as a public health issue and impedes efforts to eliminate malaria. Thus, this study aimed at investigating the prevalence and risk factors of asymptomatic malaria infection in Boricha district, Sidama region of Ethiopia.MethodsA community-based cross-sectional study was conducted in eight selected kebeles (smallest administrative unit) in Boricha district. Representative households were chosen using a multi-stage sampling technique. A total of 573 participants were included in the study. Malaria diagnosis was performed using rapid diagnostic test (RDT) and microscopy. A structured questionnaire was administered to collect socio-demographic information. Epi data 3.1 was employed for data entry, and SPSS version 25 was used for analysis.ResultsOf the 573 asymptomatic participants tested, 6.1% were found to be positive by RDT and 4.0% by microscopy. Participants aged under 5 years (AOR = 1.57, 95% CI 0.46–5.39) and 5–14 years old (AOR = 2.42, 95% CI 1.08–5.40), Insecticide-treated net utilization (AOR = 8.41; 95% CI 1.09–65.08), travel history (AOR = 6.85, 95% CI 2.32–20.26) and living in a house with windows (AOR = 2.11, 95% CI 1.02–4.36) were significantly associated with the asymptomatic malaria infection.ConclusionThe findings of this study revealed that prevalence of asymptomatic malaria infection was higher in the study area. As a result, rigorous implementation of existing interventions, such as vector control and anti-malaria drugs, is strongly recommended. In addition, devising new ones that are suited to the contextual situations is highly suggested.

Exploring the host factors affecting asymptomatic Plasmodium falciparum infection: insights from a rural Burkina Faso study

BackgroundAsymptomatic Plasmodium falciparum parasitaemia forms a reservoir for the transmission of malaria disease in West Africa. Certain haemoglobin variants are known to protect against severe malaria infection. However, data on the potential roles of haemoglobin variants and nongenetic factors in asymptomatic malaria infection is scarce and controversial. Therefore, this study investigated the associations of iron homeostasis, inflammation, nutrition, and haemoglobin mutations with parasitaemia in an asymptomatic cohort from a P. falciparum-endemic region during the high transmission season.MethodsA sub-study population of 688 asymptomatic individuals (predominantly children and adolescents under 15 years, n = 516) from rural Burkina Faso previously recruited by the NOVAC trial (NCT03176719) between June and October 2017 was analysed. Parasitaemia was quantified with conventional haemocytometry. The haemoglobin genotype was determined by reverse hybridization assays targeting a selection of 21 HBA and 22 HBB mutations. Demographics, inflammatory markers (interleukins 6 and 10, hepcidin), nutritional status (mid upper-arm circumference and body mass index), and anaemia (total haemoglobin, ferritin, soluble transferrin receptor) were assessed as potential predictors through logistic regression.ResultsMalaria parasites were detected in 56% of subjects. Parasitaemia was associated most strongly with malnutrition. The effect size increased with malnutrition severity (OR = 6.26, CI95: 2.45–19.4, p < 0.001). Furthermore, statistically significant associations (p < 0.05) with age, cytokines, hepcidin and heterozygous haemoglobin S were observed.ConclusionsAccording to these findings, asymptomatic parasitaemia is attenuated by haemoglobin S, but not by any of the other detected genotypes. Aside from evidence for slight iron imbalance, overall undernutrition was found to predict parasitaemia; thus, further investigations are required to elucidate causality and inform strategies for interventions.

Malaria rapid diagnostic tests reliably detect asymptomatic Plasmodium falciparum infections in school-aged children that are infectious to mosquitoes

BackgroundAsymptomatic malaria infections (Plasmodium falciparum) are common in school-aged children and represent a disease transmission reservoir as they are potentially infectious to mosquitoes. To detect and treat such infections, convenient, rapid and reliable diagnostic tools are needed. In this study, malaria rapid diagnostic tests (mRDT), light microscopy (LM) and quantitative polymerase chain reaction (qPCR) were used to evaluate their performance detecting asymptomatic malaria infections that are infectious to mosquitoes.MethodsOne hundred seventy asymptomatic school-aged children (6–14 years old) from the Bagamoyo district in Tanzania were screened for Plasmodium spp. infections using mRDT (SD BIOLINE), LM and qPCR. In addition, gametocytes were detected using reverse transcription quantitative polymerase chain reaction (RT-qPCR) for all qPCR-positive children. Venous blood from all P. falciparum positive children was fed to female Anopheles gambiae sensu stricto mosquitoes via direct membrane feeding assays (DMFAs) after serum replacement. Mosquitoes were dissected for oocyst infections on day 8 post-infection.ResultsThe P. falciparum prevalence in study participants was 31.7% by qPCR, 18.2% by mRDT and 9.4% by LM. Approximately one-third (31.2%) of asymptomatic malaria infections were infectious to mosquitoes in DMFAs. In total, 297 infected mosquitoes were recorded after dissections, from which 94.9% (282/297) were derived from infections detected by mRDT and 5.1% (15/297) from subpatent mRDT infections.ConclusionThe mRDT can be used reliably to detect children carrying gametocyte densities sufficient to infect high numbers of mosquitoes. Subpatent mRDT infections contributed marginally to the pool of oocyts-infected mosquitoes.Graphical

An active and targeted survey reveals asymptomatic malaria infections among high-risk populations in Mondulkiri, Cambodia

BackgroundMalaria is a mosquito-borne disease that is one of the most serious public health issues globally and a leading cause of mortality in many developing countries worldwide. Knowing the prevalence of both symptomatic and asymptomatic malaria on a subnational scale allows for the estimation of the burden of parasitaemia present in the transmission system, enabling targeting and tailoring of resources towards greater impact and better use of available capacity. This study aimed to determine the PCR-based point prevalence of malaria infection, by parasite species, among three high-risk populations in Mondulkiri province, Cambodia: forest rangers, forest dwellers, and forest goers.MethodsA cross-sectional survey was performed during the transmission season in November and December 2021. Blood samples collected on filter paper from participants (n = 1301) from all target groups were screened for Plasmodium spp using PCR.ResultsMalaria prevalence among all study participants was 6.7% for any Plasmodium species. Malaria prevalence in the forest ranger group was 8.1%, was 6.8% in forest goers, and 6.4% in forest dwellers; all infections were asymptomatic. Plasmodium vivax was detected in all participant groups, while the few Plasmodium falciparum infections were found in goers and dwellers. 81% of all infections were due to P. vivax, 9% were due to P. falciparum, 3% due to Plasmodium cynomolgi, and the rest (7%) remained undefined. Gender was associated with malaria infection prevalence, with male participants having higher odds of malaria infection than female participants (OR = 1.69, 95% CI 1.08–2.64). Passively collected malaria incidence data from the Cambodian government were also investigated. Health facility-reported malaria cases, based on rapid diagnostic tests, for the period Jan-Dec 2021 were 521 Plasmodium vivax (0.89% prevalence), 34 P. falciparum (0.06%) and four P. falciparum + mixed (0.01%)—a total of 559 cases (0.95%) for all of Mondulkiri.ConclusionThis reservoir of asymptomatic parasitaemia may be perpetuating low levels of transmission, and thus, new strategies are required to realize the goal of eliminating malaria in Cambodia by 2025.

Ultra-sensitive detection of Asymptomatic sub-microscopic Plasmodium falciparum Malaria infection amongst Children in Ngali, Center Region of Cameroon

Ultra-sensitive detection of Asymptomatic sub-microscopic Plasmodium falciparum Malaria infection amongst Children in Ngali, Center Region of Cameroon

Symptomatic and asymptomatic malaria prevalence and its determinant factors in pastoral communities of Waghemira Zone, Northeast Ethiopia: A community-based cross-sectional study.

Malaria elimination programs have also encountered numerous challenges, such as widespread asymptomatic carriers in endemic areas, which should be taken into account in malaria-control programs for effective transmission interruption. The purpose of this research was to determine the prevalence of symptomatic and asymptomatic malaria infections and associated factors, in pastoral communities. A community-based cross-sectional study was conducted among selected districts in the Waghemra Zone, Northeast Ethiopia, from September to December 2022. A structured questionnaire was employed to collect sociodemographic data and associated risk factors. Plasmodium species were detected using light microscopy and a rapid diagnostic test. Data entry and analysis were carried out using SPSS version 26 software. The association between dependent and independent variables was explored by using multivariable logistic regression analyses. A statistically significant association was declared at a p-value of <0.05. The overall prevalence of malaria was 21.2% (134/633), with the predominant Plasmodium falciparum infections accounting for 67.8% (87/134). Among asymptomatic participants, 7.5% (34/451) and 10.2% (46/451) were diagnosed by rapid diagnostic test and light microscopy, respectively. On the other hand, the prevalence of symptomatic malaria was 44.5% (81/182) and 48.4% (88/182) as diagnosed by rapid diagnostic test and light microscopy, respectively. The presence of stagnant water near the houses, the utilization of insecticide-treated mosquito nets, the number of insecticide-treated mosquito nets, and outdoor stays at night were all positively linked with the prevalence of malaria. The overall prevalence estimate for symptomatic and asymptomatic malaria was high. Malaria is still a public health problem in the study area. Malaria infection was associated with the presence of stagnant water near the houses, the utilization of insecticide-treated mosquito nets, the number of insecticide-treated mosquito nets, and outdoor stays at night. Improved access to all malaria interventions is needed to interrupt the transmission at the community level.

Malaria parasite prevalence in Sub-Saharan African migrants screened in Sweden: a cross-sectional study

Asymptomatic infections with malaria parasites are common in populations in endemic areas. These infections may persist in migrants after arrival in a non-endemic area. Screening to find and clear these infections is generally not implemented in non-endemic countries, despite a potential negative health impact. We performed a study to evaluate the Plasmodium parasite prevalence in migrants living in Sweden. Adults and children born in Sub-Saharan Africa (SSA) were invited in the study between April 2019 and June 2022at 10 different sites, mainly as part of the national Migrant Health Assessment Program in Stockholm and Västerås, Sweden. Rapid diagnostic tests (RDT) and real-time PCR were used to detect malaria parasites. Prevalence and test sensitivity were calculated with 95% confidence intervals (CI). Univariate and multivariable logistic regression were used to evaluate associations with PCR positivity. In total, 789 individuals were screened for Plasmodium spp. of which 71 (9.0%) were positive by PCR and 18 (2.3%) also by RDT. When performed during the national screening program, 10.4% was PCR positive. A high prevalence was detected in migrants with Uganda as the country of last residence, 53/187 (28.3%), and in this group the prevalence was highest in children, 29/81 (35.8%). Among the PCR positive, 47/71 (66.2%) belonged to families with at least one other member testing positive (odds ratio [OR] 43.4 (95% CI 19.0-98.9), and the time lived in Sweden ranged between 6 and 386 days. A high malaria parasite prevalence was found in migrants from SSA, particularly in children offered screening in Stockholm, Sweden during the study period. Awareness of asymptomatic malaria infection is needed and screening for malaria in migrants arriving from high endemic countries should be considered. The Swedish Research Council, Stockholm County Council and Centre for Clinical Research, Västmanland, Sweden.

Diagnostic performance of NxTek™ Eliminate Malaria-Pf test for the detection of Plasmodium falciparum in school children with asymptomatic malaria

BackgroundOne of the major roadblocks to the falciparum malaria elimination programme is the presence of a portion of the population, such as school children, with asymptomatic malaria infection. Targeting such reservoirs of infections is critical to interrupting transmission and enhancing elimination efforts. The NxTek™ Eliminate Malaria Pf test is a highly sensitive rapid diagnostic test (hsRDT) for the detection of HRP-2. However, knowledge gaps exist in Ethiopia on the diagnostic performance of hsRDT for the detection of Plasmodium falciparum in school children with asymptomatic malaria.MethodsA school-based cross-sectional study was conducted from September 2021 to January 2022 on 994 healthy school children (aged 6–15 years). Finger-pricked whole blood samples were collected for microscopy, hsRDT, conventional RDT (cRDT or SD Bioline Malaria Ag Pf/P.v), and QuantStudio™ 3 Real—Time PCR system (qPCR). The hsRDT was compared to cRDT and microscopy. qPCR and microscopy were used as reference methods.ResultsThe prevalence of Plasmodium falciparum was 1.51%, 2.2%. 2.2% and 4.52%, by microscopy, hsRDT, cRDT and qPCR, respectively. Using qPCR as reference, the sensitivity of hsRDT was higher (48.89%) than the microscopy (33.3%), and showed 100% specificity and a positive predictive value (PPV). Microscopy showed similar specificity and PPV as hsRDT. Using microscopy as a reference, the diagnostic perforrmances of both hsRDT and cRDT were similar. Both RDTs demonstrated identical diagnostic performances in both comparison methods.ConclusionshsRDT has the same diagnostic performance as cRDT but improved diagnostic characteristics than microscopy for detection of P. falciparum in school children with asymptomatic malaria. It can be a useful tool for the national malaria elimination plan of Ethiopia.

Plasmodium falciparum adapts its investment into replication versus transmission according to the host environment.

The malaria parasite life cycle includes asexual replication in human blood, with a proportion of parasites differentiating to gametocytes required for transmission to mosquitoes. Commitment to differentiate into gametocytes, which is marked by activation of the parasite transcription factor ap2-g, is known to be influenced by host factors but a comprehensive model remains uncertain. Here, we analyze data from 828 children in Kilifi, Kenya with severe, uncomplicated, and asymptomatic malaria infection over 18 years of falling malaria transmission. We examine markers of host immunity and metabolism, and markers of parasite growth and transmission investment. We find that inflammatory responses associated with reduced plasma lysophosphatidylcholine levels are associated with markers of increased investment in parasite sexual reproduction (i.e. transmission investment) and reduced growth (i.e. asexual replication). This association becomes stronger with falling transmission and suggests that parasites can rapidly respond to the within-host environment, which in turn is subject to changing transmission.

Prevalence of asymptomatic malaria infection by microscopy and its determinants among residents of Ido-Ekiti, Southwestern Nigeria.

Asymptomatic malaria infections have received less attention than symptomatic malaria infections in major studies. Few epidemiological studies on asymptomatic malaria infections have often focused on pregnant women and children under-five years of age as the most vulnerable groups. However, there is limitation on data regarding asymptomatic infections among the old adult populations, particularly in the study area. Therefore, this study determined the prevalence of asymptomatic malaria infection by microscopy and its determinants among residents of Ido- Ekiti, Southwestern Nigeria. A hospital-based cross-sectional study was conducted between July and September 2021 among 232 consenting apparently healthy individuals aged 40 years and above who were recruited during a free health screening program using a standardised interviewer-administered questionnaire. The questionnaire sought information on respondents' socio-demographics, presence and types of co-morbidity, and the prevention methods being adopted against malaria infection. Venous blood samples were collected and processed for asymptomatic infections using Giemsa-stained blood smear microscopy. Data were analysed using SPSS version 21. Multivariate logistic regression was used to identify factors associated with asymptomatic infections. Of the total 232 respondents, 19.0% (48/232) were confirmed to be infected with Plasmodium falciparum (95% confidence interval (CI): 14.1% - 24.6%). Lack of formal education (Adjusted odds ratio (AOR): 5.298, 95% (CI): 2.184-13.997), being diabetic (AOR: 4.681, 95% CI: 1.669-16.105), and not sleeping under Long Lasting Insecticide Net (LLINs) (AOR: 4.594, 95% CI: 1.194-14.091), were the determinants of asymptomatic Plasmodium falciparum infection. The prevalence of asymptomatic Plasmodium falciparum was 19%. Lack of formal education, being diabetic, and not sleeping under LLINs were the determinants of asymptomatic infections.

Cytokine response in asymptomatic and symptomatic Plasmodium falciparum infections in children in a rural area of south-eastern Gabon.

Plasmodium falciparum is a parasite that causes asymptomatic or symptomatic malaria infections in humans depending on various factors. These infections are also a major cause of anemia in intertropical countries such as Gabon. Past studies have clearly demonstrated that inflammatory markers such as cytokines play a key role in the pathogenesis of malaria disease. However, the clinical manifestations of severe malaria vary according to the level of transmission and more information is needed to gain a better understanding of the factors involved. As such, the objective of this study was to investigate the circulating levels of nine cytokines in asymptomatic and symptomatic P. falciparum infections in Gabonese children and their roles in the pathogenesis of anemia. Blood samples were collected from 241 children aged 3 to 180 months in Lastourville, south-eastern Gabon. Diagnosis of P. falciparum infection was performed using Rapid Diagnosis Tests, microscopy and nested PCR. Levels in the plasma of the Th1 (IFN-γ, TNF-α, IL-6 and IL-12p70), Th17 (IL-17A and IL-22) and Th2 (IL-10, IL-4 and IL-13) cytokines were measured by ELISA. Data showed that IL-6, IFN-γ, IL-12p70, IL-10, and IL-13 levels were significantly higher in children with symptomatic P. falciparum infection compared to uninfected children. IL-10 levels were significantly higher in symptomatic children than in asymptomatic children, who had moderately increased levels compared to uninfected controls. Moreover, only IL-10 and IL-6 levels were significantly higher in children with severe malarial anemia compared to children with uncomplicated malaria who had significantly lower IL-10 levels than children with moderate malarial anemia. These data indicate that the progression of P. falciparum infection towards an advanced stage in children is accompanied by a significant increase in type Th1 and/or Th2 cytokines. These inflammatory mediators could serve as potential predictors of anemia for malaria patients.

The Association Between Asymptomatic Placental Malaria Infection and Pregnancy Outcome in Delta State, Nigeria

Purpose: Parturients in the Sub-Saharan African are susceptible to malaria disease due to their reduced immunity during pregnancy. Asymptomatic placental malaria causes neonatal and maternal mortalities, preterm deliveries as well as low birth weight babies. Current studies on malaria in pregnancy indicated that the risk factors are location specific, and there are limited studies in Nigeria on asymptomatic placental malaria and pregnancy outcome (babies birth weight and delivery term). The purpose of this study was to determine the association between asymptomatic placental malaria infection and pregnancy outcome (baby’s birth weight and delivery term) among parturients in Asaba, Delta State, Nigeria.&#x0D; Methodology: Quantitative methodology with primary and secondary healthcare facility data from 483 subjects aged 18–49 years generated from four healthcare facilities between May and July 2021 was used for this study. The Socio-Ecological Model framework was used to describe how parturients can achieve enhanced pregnancy outcome through the utilization of multi-levels of supports to enhance the compliance of pregnant women to the existing malaria interventions. The research questions and hypotheses were tested with the binomial logistic regression.&#x0D; Result:  The findings showed a statistically significant association between baby’s birth weight, delivery term and placental malaria parasitemia (PMP), in the study population. Also, the identified risk factor for baby’s birth weight in this study was gravidae, while that of delivery term was age groups, gravidae, ITN frequent use and ANC attendance.&#x0D; Unique Contribution to Theory, Policy and Practice: The findings of this study could inform malaria control policymaking in Asaba and Delta State on tracking and treating asymptomatic malaria among underserved pregnant women accessing antenatal services to improve baby’s birth weight, delivery term, and the associated complications.